Barack Obama has ordered a review of the supply of military hardware to local US police departments amid concern about the deployment of heavily-armed “robo-cop” officers during protests over the shooting dead of a black teenager.

America was shocked by the images of protesters in Missouri being confronted by combat-ready police officers in body armour, equipped with semi-automatic weapons and sniper’s rifles, backed up by armoured vehicles.

The racially-charged protests were triggered in the St Louis suburb of Ferguson after the fatal shooting by a white police officer of Michael Brown, an unarmed African-American 18-year-old.

Mr Obama has now instructed his officials to review the post-9/11 the strategy of distributing Pentagon weaponry and equipment such as body armour, mine-resistant trucks, silencers and automatic rifles to police forces across the country.

The president has ordered them to assess whether to continue supplying the material and, if so, whether the police departments are receiving the training to use the equipment appropriately.

The announcement came as Brown’s parents prepare to bury their son on Monday morning at a funeral service that could become the focus for fresh unrest.

“There is a big difference between our military and our local law enforcement, and we don’t want those lines blurred,” Mr Obama said in the aftermath of the shooting. “That would be contrary to our traditions.”

The review will be conducted by staff from the White House, Pentagon and Homeland Security and Justice departments - a sign said officials about how serious the instructions were from Mr Obama.

The federal programmes providing billions of dollars of funding for state and local police departments to purchase military equipment were launched in the wake of the September 11, 2001 terror attacks.

The then Bush administration viewed law enforcement departments as the frontline of the domestic the war on terror.

Eric Holder, who oversees law enforcement in the US as Mr Obama’s attorney general, said that the equipment “flowed to local police forces because they were increasingly being asked to assist in counterterrorism”.

But he said “displays of force in response to mostly peaceful demonstrations can be counterproductive,” and so “it makes sense to take a look at whether military-style equipment is being acquired for the right purposes and whether there is proper training on when and how to deploy it”.

Peter King, a Republican congressman and prominent security hardliner, dismissed that criticism and said he had seen nothing to justify scaling back federal police grants.

He told The New York Times there was no evidence that giving the police heavy weaponry and equipment worsened the situation in Ferguson or led to abuses elsewhere.